Detune Ltd iYM2151, £24.49

Compatibility: iPad (requires iOS 4.2 or later)

It’s not cheap, but this app is a complete emulation of Yamaha’s YM2151 single-chip FM synthesis implementation that was used to create the sound of many ‘80s video games. It has four operators, eight voices and three LFOs and is completely programmable.

Szymon Kaliski MicroTones, £1.99

Compatibility: iPhone, iPod touch, iPad (requires iOS 5.0 or later)

A microtonal synth that can play back up to 30 sinewaves at a time. Place a new one by touching the screen and then make volume and frequency adjustments to change the soundscape. The app promises to make it easy to create ambient atmospheres and drones.

Kymatica BitWiz Audio Synth, £1.99

Compatibility: iPhone, iPod touch, iPad (requires iOS 4.3 or later)

It might not look much like a music-making tool, but BitWiz is capable of translating C-like code expressions into lo-fi 8-bit generative audio in real-time. If none of that makes sense then this probably isn’t the app for you, though it does come with some examples to get you started.

Eiji Nishidai iToneMaker Morse Edition, Free

Compatibility: iPhone, iPod touch, iPad (requires iOS 4.2 or later)

OK, it’s first and foremost a ringtone maker, but iToneMaker looks to have some proper music software-style features and also offers WAV and AIFF export. As such, it might provide some fast inspiration, and because it’s free, you’ve got nothing to lose by trying it.